Electronic component with reduced inductive coupling

ABSTRACT

The invention relates to an electronic component comprising a package PACK including input pins PIi and output pins PSj, and an integrated circuit IC, encased in the package PACK, which integrated circuit is provided with input contact pads CIi and output contact pads CIj, which are connected, respectively, to the input pins PIi and the output pins PSj of the package PACK by conducting wires WIi and WSj. In accordance with the invention, each current path connecting an input contact pad CIi to an output contact pad CIj comprises a buffer element Bi having a high input impedance. Said high input impedance of the buffers substantially reduces the value of the current Ii flowing through the conducting wires WIi connecting the input pins PIi to the input contact pads CIi, and hence the inductive coupling between said conducting wires.

FIELD OF THE INVENTION

The invention relates to an electronic component comprising:

a package having N input pins and M output pins, which are intended,respectively, to receive and supply data signals, and

an integrated circuit, which is encased in said package, and whichincludes N input contact pads and M output contact pads, which areconnected, respectively, to the N input pins and M output pins byconducting wires, which integrated circuit includes a plurality ofcurrent paths, which are each used to connect an input contact pad to anoutput contact pad.

BACKGROUND

It has been observed by the current applicant that during operation ofsuch an electronic component, certain output pins supply data signalscontaining parasitic components, which do not correspond to any of thedata signals received by those input contact pads which are electricallyconnected to said output pins. The current applicant has concluded thatsuch phenomena are caused by inductive coupling between the variousconducting wires connecting the input pins to the input contact pads:due to mutual inductance effects, components representative of signalscarried by wires adjoining the wire under consideration are introducedinto the signal carried by said wire under consideration. Theseadditional components are contained in the signal which will be suppliedby the output pin(s) which is (are) electrically connected to the wireunder consideration, and will then constitute a parasitic component insaid signal. The extent of the effects of mutual inductance is wider asthe frequency of the data signals is higher.

SUMMARY

It is an object of the invention to overcome this drawback to a largeextent by providing an electronic component wherein the effect of theinductive couplings between conducting wires connecting the input pinsto the input contact pads are reduced substantially.

Indeed, in accordance with the invention each current path in anelectronic component in accordance with the opening paragraph comprisesa buffer element, exhibiting a high input impedance.

In such an electronic component, the high input impedances of saidbuffers cause the value of the currents flowing through the currentpaths upstream from the buffers, and hence the value of the currentsflowing through the conducting wires connecting the input pins to theinput contact pads, to be negligibly small. The extent of the mutualinductance phenomena occurring between adjacent wires, which is directlyproportional to the value of the currents flowing through these wires,is thus reduced considerably, thereby precluding that a wire induces anadditional component of substantial amplitude in the signal travelingthrough an adjacent wire. By virtue of the invention, each output pinthus supplies a signal which is representative only of signalcontributions arriving at the input contact pads which are effectivelyelectrically connected to said output pin, which signal consequentlydoes not contain the parasitic component described hereinabove.

The buffers are advantageously composed of amplifiers, whose inputimpedance is naturally high, for example an assembly based on aDarlington-type structure.

In accordance with a particular embodiment of the invention, each inputcontact pad is connected to a buffer. This ensures that all currentsflowing through the conducting wires connecting the input pins to inputcontact pads are negligibly small.

Although the invention can be employed in any type of electroniccomponent comprising at least two input pins, the invention isadvantageously used in multiplexers intended to receive and supplysignals at very high frequencies, for example in the gigahertz range.

Thus, in a preferred embodiment of the invention, an electroniccomponent as described hereinabove includes:

M buffer elements, each having an input and an output, the latter beingconnected to one of the output contact pads,

M switching stages, each comprising N switches, each switch having afirst terminal and a second terminal, the first terminal being connectedto one of the input contact pads, and all the second terminals beingjointly connected to the input of one of the buffers, and

control means for controlling the switching stages, which are arrangedin such a way that only one of the switches included in a same switchingstage can be conductive at any given instant.

This structure, which is used for multiplexing, by selecting M datasignals from the N signals received on the input pins in order to directthese signals towards the M output pins, only requires M buffer, insteadof the N buffers, which would have been necessary in accordance with theparticular embodiment described hereinabove.

DETAILED DESCRIPTION

These and other aspects of the invention will be apparent from andelucidated with reference to the non-limitative exemplary embodimentdescribed in FIG. 1, which is a functional diagram showing an electroniccomponent in accordance with a preferred embodiment of the invention.This component comprises:

a package PACK provided with four input pins PIi (i=1 to 4) and twooutput pins PSj

(j=1 or 2), which are used, respectively, to receive and to supply datasignals, and

an integrated circuit IC, encased in the package PACK, and provided withfour input contact pads CIi (i=1 to 4) and two output contact pads CSj(j=1 or 2), which are connected, respectively, to four input pins PIiand two output pins PSj by conducting wires WIi.

In this example, the integrated circuit IC comprises:

two buffer elements B1 and B2, each having an input and an output, thelatter being connected to one of the output contact pads CS1 and CS2,

two switching stages SW1 and SW2, each comprising four switches, andeach switch having a first terminal and a second terminal, the firstterminal being connected to one of the input contact points CIi (i=1 to4), and all the second terminals being jointly connected to the input ofone of the buffers B1 or B2, and

control means CNT for controlling the switching stages SW1 and SW2,which are arranged in such a way that only one of the switches includedin a same switching stage can be conductive at any given instant.

To this end, the control means CNT supply two control signals CNT1 andCNT2 to the switching stages SW1 and SW2, which control signals arecoded on four bits, and one of said control signals is in the activemode, for example at a logic level 1, at a given instant.

The switches included in the switching stages SW1 and SW2 can beimplemented by means of MOS-type transistors or any other equivalentcomponents. In an electronic component deprived of buffers B1 and B2, iffor example, the control means CNT activate that switch of the firstswitching stage SW1 which is arranged between the input contact pad C11and the output contact pad CS1, thereby producing a current path betweenthese contact pads, then a current 11 flows through the conducting wireW11. If the control means CNT simultaneously activate that switch of thesecond switching stage SW2, which is arranged between the input contactpad C12 and the output contact pad CS2, thereby producing a furthercurrent path between the contact points, then a current 12 flows throughthe conducting wire W12. The two currents 11 and 12 then create a mutualinductance between the conducting wires W11 and W12, and the signalsupplied by the output pin PS1 will contain a parasitic component thatis representative of the current 12, while the signal supplied by theoutput pin PS2 will contain a parasitic component that is representativeof the current 11.

In the electronic component in accordance with the invention, thebuffers B1 and B2, which exhibit a large input impedance, render thecurrents 11 and 12 negligibly small, and thereby considerably reduce theeffects of the mutual inductance phenomenon occurring between theconducting wires W11 and W12. The output signals supplied by the outputpins PS1 and PS2 thus will contain no significant parasitic componentrepresentative of, respectively, the currents 12 and 11.

In this preferred embodiment of the invention, the buffers B1 and B2 arearranged in such a way that one of them is present in all possiblecurrent paths between the input contact pads and the output contactpads, so that the provision of a buffer downstream from each inputcontact pad can be dispensed with, thus enabling the necessary number ofbuffers to be reduced by a factor of M/N=½.

Mutual inductance phenomena of the type described hereinabove may occurbetween the conducting wires WSj interconnecting the output contact padsCSj and the output pins PSj. However, in many types of applications,such as the multiplexing carried out by the electronic componentdescribed in this exemplary embodiment of the invention, the output pinsPSj will be smaller in number than the input pins PIi. It will thus bepossible, in principle, to space out these output pins PSj bydistributing them at the periphery of the package PACK, so that themutual inductance between the conducting wires WSj cannot havesignificant effects owing to the space between said conducting wires. Ifsuch a distribution is impossible, the output pins PSj willadvantageously be connected to buffers having a high input impedance,arranged outside the package PACK, and not shown in the drawing.

What is claimed is:
 1. An electronic component comprising: a packagehaving N input pins and M output pins, which are intended, respectively,to receive and supply data signals, and an integrated circuit, which isencased in said package, and which includes N input contact pads and Moutput contact pads, which are connected, respectively, to the N inputpins and M output pins by conducting wires, which integrated circuitincludes a plurality of current paths, which are each used to connect aninput contact pad to an output contact pad, in which electroniccomponent each current path comprises a buffer element, exhibiting ahigh input impedance, wherein each buffer element substantially reducesa mutual inductance phenomena occurring between adjacent conductingwires.
 2. An electronic component as claimed in claim 1, wherein eachinput contact pad is connected to a buffer.
 3. An electronic componentas claimed in claim 1, wherein the integrated circuit includes: M bufferelements, each having an input and an output, the latter being connectedto one of the output contact pads, M switching stages, each comprising Nswitches, each switch having a first terminal and a second terminal, thefirst terminal being connected to one of the input contact pads, and allthe second terminals being jointly connected to the input of one of thebuffers, and control means for controlling the switching stages, whichare arranged in such a way that only one of the switches included in asame switching stage can be conductive at any given instant.
 4. Anelectronic component as claimed in claim 1, wherein the buffers areamplifiers.